KR102503175B1 - Vessel using ammonia as fuel - Google Patents

Abstract

A ship according to the present invention is propelled by using ammonia as fuel, and includes an ammonia supply line for supplying ammonia stored in an ammonia storage tank to an ammonia engine; a return gas recovery line for transferring return gas discharged from the ammonia engine and mixed with oil to the ammonia supply line; a collection tank separating the oil mixed with the return gas flowing through the return gas recovery line; an exhaust gas discharge line having an SCR reducing nitrogen oxides in exhaust gas discharged from the ammonia engine; and a boil-off gas supply line for supplying boil-off gas generated in the ammonia storage tank to the SCR.

Description

Vessel using ammonia as fuel}

The present invention relates to a ship using ammonia as fuel.

In general, ships use a diesel engine that generates driving force using diesel oil, a gas engine that generates driving force using gas such as LNG, and a dual fuel engine that generates driving force by mixing diesel oil and gas. Proceed using

Recently, as the demand for eco-friendly/high-efficiency engines increases due to the strengthening of IMO environmental regulations, research on propulsion systems using various fuels is being actively conducted.

Ammonia is attracting attention as an environmentally friendly fuel because it does not contain carbon. However, ammonia has relatively low combustion efficiency compared to conventionally used fuels, and ammonia slip phenomenon in which ammonia that is not burned inside the engine is mixed in exhaust gas and discharged to the atmosphere may occur, and nitrogen oxides ( There was a problem that the emission of NOx) increased and polluted the environment.

Conventionally, SCR (Selective Catalytic Reduction), which sprays ammonia into exhaust gas, has been used to treat nitrogen oxides contained in exhaust gas. As an ammonia source, urea solution, which is less toxic than ammonia and is easy to handle, was used. However, in this case, there is a limitation in that urea water must be regularly purchased and used, and additional facilities are required for storing urea water and decomposing it at high temperature to convert it into ammonia.

The present invention was created to solve the above problems of the prior art, and an object of the present invention is to treat ammonia and nitrogen oxides in exhaust gas discharged from an engine that burns ammonia as a ship propulsion using ammonia as fuel. is to provide a vessel capable of

A ship according to one aspect of the present invention is a ship propelled by using ammonia as fuel, an ammonia supply line for supplying ammonia stored in an ammonia storage tank to an ammonia engine, and a return gas discharged from the ammonia engine and mixed with oil. A return gas recovery line delivered to the ammonia supply line, a collection tank for separating the oil mixed with the return gas flowing through the return gas recovery line, and an SCR for reducing nitrogen oxides in the exhaust gas discharged from the ammonia engine An exhaust gas discharge line provided, and a boil-off gas supply line for supplying boil-off gas generated in the ammonia storage tank to the SCR.

Specifically, the ammonia supply line includes a heat exchanger for heating ammonia as heat and a high-pressure pump, and the return gas recovery line includes a return gas cooler provided downstream of the collection tank, and the high-pressure pump It may be connected to the ammonia supply line upstream.

Specifically, the vessel may further include a control unit for operating the SCR when the amount of nitrogen oxides contained in the exhaust gas is greater than a predetermined value.

Specifically, the exhaust gas discharge line is provided downstream of the SCR and further includes a catalyst unit that decomposes ammonia in the exhaust gas, and the ship, when the amount of ammonia contained in the exhaust gas is greater than a predetermined value, A control unit for operating the catalyst unit may be further included.

Specifically, the vessel may further include a control unit for adjusting the flow rate of the boil-off gas supplied to the SCR through the boil-off gas supply line according to the amount of ammonia contained in the exhaust gas.

Specifically, the vessel further includes a boil-off gas treatment unit for recovering boil-off gas generated in the ammonia storage tank, and the control unit, when the amount of ammonia contained in the exhaust gas is greater than a predetermined value, the boil-off gas treatment unit It may be to increase the flow rate of boil-off gas supplied to.

Specifically, the ship, when the return gas supply line for delivering gaseous ammonia separated from the collection tank to the boil-off gas supply line, and the flow rate of boil-off gas generated in the ammonia storage tank is less than a predetermined value A control unit for increasing the flow rate of ammonia supplied through the return gas supply line may be further included.

Specifically, the ship is supplied to the ammonia branch line according to the ammonia branch line branching from the ammonia supply line and vaporizing ammonia and passing it to the boil-off gas supply line, and the flow rate of the return gas discharged from the ammonia engine A control unit for adjusting the flow rate of ammonia may be further included.

The vessel according to the present invention treats nitrogen oxides included in the exhaust gas of an ammonia engine in the SCR, but omits the urea water storage and supply system for treating nitrogen oxides by using ammonia for fuel in the SCR. and improve the energy efficiency of the entire system.

In addition, the ship according to the present invention is configured to use the gaseous ammonia separated from the boil-off gas generated in the ammonia storage tank and the return gas discharged from the ammonia engine in the SCR, so that the internal pressure of the ammonia storage tank can be managed, and the ammonia Energy required for vaporization can be saved.

1 is a conceptual diagram showing a system for propulsion using ammonia in a ship according to an embodiment of the present invention.
Figure 2 is a flow chart showing a control embodiment according to the operation of the ammonia engine in the ship shown in Figure 1.

Objects, specific advantages and novel features of the present invention will become more apparent from the following detailed description and preferred embodiments taken in conjunction with the accompanying drawings. In adding reference numerals to components of each drawing in this specification, it should be noted that the same components have the same numbers as much as possible, even if they are displayed on different drawings. In addition, in describing the present invention, if it is determined that a detailed description of related known technologies may unnecessarily obscure the subject matter of the present invention, the detailed description will be omitted.

In the following, it is noted that high pressure, low pressure, high temperature, low temperature, high load, low load, and flow rate are relative and do not represent absolute values.

Hereinafter, ships include not only ammonia carriers that transport ammonia as cargo, but also container ships that can be propelled using ammonia, merchant ships, ships that can produce natural gas in the ocean, and offshore structures including gas platforms and offshore floating objects. Note that it is an expression of

Hereinafter, boil off gas (BOG) may mean gaseous ammonia as naturally vaporized or forcibly vaporized ammonia. However, boil-off gas may be used in the sense of including not only gaseous ammonia but also boil-off gas of liquefied ammonia. In addition, it should be noted that hereinafter, ammonia may be used as a term encompassing both a liquid state and a naturally vaporized or forcibly vaporized gaseous state.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 1, a vessel according to an embodiment of the present invention will be described.

The vessel according to the present embodiment includes an ammonia storage tank 10, an ammonia engine 20, an SCR 23, a boil-off gas compressor 30, a boil-off gas treatment unit 31, an ammonia supply line L10, and exhaust gas discharge. It includes a line (L20), a boil-off gas supply line (L30), a return gas recovery line (L40), and the like. Hereinafter, each line may further include a valve for controlling the flow rate of the fluid flowing through the corresponding line.

The ammonia storage tank 10 may be disposed inside the hull. For example, three or four ammonia storage tanks 10 may be provided at the front of the engine room. The ammonia storage tank 10 is, for example, a membrane-type tank, but is not limited thereto, and the type is not particularly limited to various forms such as a stand-alone tank.

The ammonia supply line (L10) has one end connected to the ammonia storage tank 10 and the other end connected to the ammonia engine 20 to supply liquid ammonia stored in the ammonia storage tank 10 to the ammonia engine 20. there is. The ammonia supply line L10 may extend to the lower end of the ammonia storage tank 10 and be immersed in liquid ammonia, and may include a pump 11 for withdrawing ammonia.

Although not shown, the pump 11 may be provided at the bottom of a pump tower disposed inside the ammonia storage tank 10, and may be installed to be submerged in liquid ammonia stored in the ammonia storage tank 10. The pump 11 may be installed to be spaced apart from the inner bottom surface of the ammonia storage tank 10, and may be provided in plurality. The pump 11 may pressurize and supply liquid ammonia in a heat exchanger 12 to be described later to a pressure at which liquid ammonia may not be vaporized even when heated to a temperature required by the ammonia engine 20 .

The ammonia supply line L10 may further include a first valve V1, a heat exchanger 12, and a high pressure pump 13. The first valve (V1) can control the flow rate of ammonia supplied through the ammonia supply line (L10) together with the second valve (V2) provided on the ammonia branch line (L11) to be described later. The heat exchanger 12 and the high-pressure pump 13 are provided downstream of the first valve V1 and can treat and supply ammonia supplied through the ammonia supply line L10 under conditions required by the ammonia engine 20.

The heat exchanger 12 may receive liquid ammonia and heat it to a temperature higher than that required by the ammonia engine 20 . In the ammonia engine 20, a return gas containing ammonia that has not reacted during the combustion process and oil inside the ammonia engine 20 may be discharged, and the oil may have a relatively higher freezing point than ammonia. The return gas may rejoin the ammonia supply line L10 and be re-supplied to the ammonia engine 20. When the liquid ammonia heated in the heat exchanger 12 and the return gas are mixed, the oil contained in the return gas freezes. It can be supplied to the ammonia engine 20 without any problems. For example, the heat exchanger 12 may heat ammonia by exchanging heat with liquid ammonia with a heat exchanger other than ammonia, and preferably, the heat may be a non-explosive fruit such as glycol water. Ammonia heated in the heat exchanger 12 may be supplied to the high-pressure pump 13.

The high-pressure pump 13 supplies ammonia to the ammonia engine 20 and can pressurize the ammonia at a relatively high pressure compared to the pump 11 described above. For example, the pump 11 may pressurize ammonia at a pressure of about 10 to 30 bar, and the high pressure pump 13 may pressurize ammonia at a pressure of about 60 to 100 bar.

The ammonia supply line (L10) may further include an ammonia branch line (L11) branched from the ammonia supply line (L10) and connected to a boil-off gas supply line (L30) or SCR (23) to be described later. A second valve V2 and a vaporizer 14 may be provided in the ammonia branch line L11. Preferably, the ammonia branch line (L11) may branch from the upstream of the first valve (V1) of the ammonia supply line (L10) and be connected to the boil-off gas supply line (L30). Liquid ammonia supplied to the ammonia branch line L11 may be supplied to the vaporizer 14, forcibly vaporized, and supplied to the boil-off gas supply line L30. The vaporizer 14 may forcibly vaporize at least a portion of ammonia by heating ammonia with a heat medium, and preferably vaporize all of the ammonia using seawater or steam produced inside the hull.

The ammonia engine 20 includes an internal combustion engine for generating propulsion by burning ammonia or generating electric power or other power. Preferably, the ammonia engine 20 generates power by burning ammonia, and transfers the generated power to a propeller (not shown) connected to the ammonia engine 20 to propel the ship. For example, the ammonia engine 20 may be a heterogeneous fuel engine capable of generating driving force by burning two or more types of fuels containing ammonia, and may be provided as a 2-stroke or 4-stroke.

The ammonia engine 20 discharges return gas in which some of the ammonia supplied by the operating mechanism returns without being injected. The ammonia engine 20 receives ammonia through the ammonia supply line L10, and during operation of the ammonia engine 20, a return gas mixed with ammonia and sealing oil for maintaining the internal pressure of the high-pressure injector is supplied to the return gas recovery line ( L40) can be discharged.

The return gas recovery line L40 may transfer the return gas discharged from the ammonia engine 20 to the ammonia supply line L10 and recycle it. The return gas is mostly composed of liquid ammonia and vaporized ammonia, but since oil is mixed, it is better to resupply it to the ammonia engine 20 and use it as fuel rather than recovering it to the relatively low temperature ammonia storage tank 10. desirable. The return gas recovery line (L40) may have one end connected to the ammonia engine 20 and the other end connected to the ammonia supply line (L10), preferably downstream or high pressure of the heat exchanger 12 in the ammonia supply line (L10). It is connected upstream of the pump 13 to supply return gas.

The return gas recovery line L40 may further include a return gas cooler 40 and a collection tank 41 . The return gas cooler 40 may cool ammonia that has not been injected while passing through the ammonia engine 20 but has been heated to a relatively high temperature to a temperature suitable for supplying the ammonia to the ammonia engine 20 . The return gas cooler 40 may cool the return gas by exchanging heat with the return gas, preferably the fruit may be seawater.

Although not shown, the collection tank 41 may be provided on the return gas recovery line L40 or connected to the return gas recovery line L40 through the return gas branch line L41. The collection tank 41 may receive the return gas through the return gas recovery line L40 and temporarily store it. The ammonia engine 20 may discharge return gas even when the operation is stopped normally, and the amount of return gas discharged may vary depending on the operating state of the ammonia engine 20 . The collection tank 41 is for temporarily storing the return gas recovered when the ammonia engine 20 is stopped in a high-pressure condition capable of maintaining a liquid state at room temperature instead of transferring it to the ammonia storage tank 10. In addition, the collection tank 41 may be used to separate nitrogen gas and liquid ammonia from a nitrogen purge operation that occurs when the ammonia engine 20 is stopped. The flow rate of the return gas supplied to the collection tank 41 may be adjusted by the seventh valve V7.

When the return gas is supplied into the collection tank 41 , phases of the return gas may be separated in the collection tank 41 . For example, liquid ammonia contained in the return gas is relatively heavy compared to gaseous ammonia and oil, so it collects at the bottom of the collection tank 41, oil forms a layer on the liquid ammonia layer, and gaseous ammonia is collected in the collection tank. It can be gathered at the top of (41). The collection tank 41 may transfer liquid ammonia and oil, preferably liquid ammonia, back to the return gas recovery line L40. The collection tank 41 may deliver gaseous ammonia to a boil-off gas supply line L30 to be described later through a return gas supply line L42 connected to an upper portion of the collection tank 41. An eighth valve (V8) is provided in the return gas supply line (L42), so that the mixture of gaseous ammonia and boil-off gas supplied through the boil-off gas supply line (L30) can be adjusted.

The return gas discharged from the ammonia engine 20 passes through the return gas branch line L41 through the collection tank 41 to separate at least a portion of gaseous ammonia, and then through the return gas cooler 40 through the ammonia supply line L10. ) can be supplied. At this time, all of the gaseous ammonia in the return gas may not be separated in the collection tank 41, and the return gas may not pass through the collection tank 41, so the gaseous ammonia mixed in the return gas is the return gas At least a part of it may be condensed or liquefied in the cooler 40 . The return gas containing liquid ammonia may be mixed with liquid ammonia supplied through the ammonia supply line L10 and re-supplied to the ammonia engine 20 through the high-pressure pump 13.

The ammonia engine 20 produces exhaust gas containing nitrogen oxides as a result of ammonia combustion. The exhaust gas discharge line L20 through which the exhaust gas generated in the ammonia engine 20 flows may connect the ammonia engine 20 and the exhaust gas discharge unit 25 . The exhaust gas discharge unit 25 may be configured to discharge exhaust gas outboard like a chimney provided in a ship.

The exhaust gas discharge line L20 may include a sensor that detects nitrogen oxides and ammonia included in the exhaust gas and transmits the information. Exhaust gas generated from the ammonia engine 20 may include not only nitrogen oxides due to oxidation of ammonia, but also ammonia that cannot burn and slips in the ammonia engine 20 . A nitrogen oxide sensor (or NOx sensor, 21) and an ammonia sensor (or NH ₃ sensor, 22) are provided downstream of the ammonia engine 20 in the exhaust gas discharge line (L20) to determine the amount of nitrogen oxides and ammonia in the exhaust gas. Information can be transmitted to a control unit (not shown) to be described later.

The exhaust gas discharge line L20 may include an SCR 23 for reducing nitrogen oxides in the exhaust gas. The SCR 23 may provide a passage through which a catalyst for reducing nitrogen oxides and exhaust gas communicate therein, and by receiving ammonia and bringing it into contact with the exhaust gas, nitrogen oxides included in the exhaust gas may be reduced to nitrogen. can The SCR (23) is provided on the exhaust gas discharge line (L20) and may perform an operation of contacting ammonia with the exhaust gas or stop the contact and flow the exhaust gas as it is, but is not limited thereto. As shown in FIG. 1, the SCR 23 receives at least a portion of the exhaust gas through the third valve V3 provided in the exhaust gas discharge line L20, reduces nitrogen oxides in the exhaust gas, and then exhausts it again. It may be delivered to the gas discharge line (L20). The third valve V3 may be a three-way valve.

The SCR 23 may receive the boil-off gas from the boil-off gas supply line L30 and inject it into the exhaust gas. Alternatively, it may be to receive forcibly vaporized ammonia from the ammonia branch line L11 and inject it into the exhaust gas. The SCR 23 may operate when the amount of nitrogen oxides included in the exhaust gas flowing through the exhaust gas discharge line L20 is greater than a predetermined value. For example, when a ship is in a nitrogen oxide emission regulation area and the amount of nitrogen oxide in the exhaust gas is higher than the emission standard, the SCR 23 can operate and the exhaust gas supplied to the exhaust gas discharge unit 25 may contain nitrogen oxides in amounts less than the emission standards.

The exhaust gas discharge line L20 may include a catalyst unit 24 for reducing ammonia in the exhaust gas. The catalyst unit 24 may provide a passage through which a catalyst for decomposing ammonia and exhaust gas communicate therein, and ammonia contained in the exhaust gas may be decomposed into nitrogen and hydrogen by contacting the exhaust gas with the catalyst. there is. Catalyst unit 24 is provided on the exhaust gas discharge line (L20), may perform an operation of contacting the exhaust gas with the catalyst, or may be stopped by blocking the contact and flowing the exhaust gas as it is, but is not limited thereto. . As shown in FIG. 1, the catalyst unit 24 receives at least a portion of the exhaust gas through the fourth valve V4 provided in the exhaust gas discharge line L20, decomposes ammonia in the exhaust gas, and then exhausts it again. It may be delivered to the gas discharge line (L20). The fourth valve V4 may be a three-way valve.

The catalyst unit 24 may be supplied with ammonia slipped from the ammonia engine 20, ammonia slipped from the SCR 23, and boil-off gas supplied from a boil-off gas branch line L32 to be described later, and process them. . The catalyst unit 24 may operate when the amount of ammonia contained in the exhaust gas flowing through the exhaust gas discharge line L20 is greater than a predetermined value. For example, when the ship is in an ammonia emission regulation area and the amount of ammonia in the exhaust gas is greater than the emission standard, the catalyst unit 24 may operate and the exhaust gas supplied to the exhaust gas discharge unit 25 It can contain less ammonia than the emission standard.

Boiled gas supply line (L30) has one end connected to the ammonia storage tank 10, the other end may be connected to the SCR (23) or the exhaust gas discharge line (L20). Preferably, the boil-off gas supply line (L30) can take out the boil-off gas of ammonia naturally evaporated in the ammonia storage tank 10 and supply it to the SCR (23), and the boil-off gas is the nitrogen oxides contained in the exhaust gas. can be used for reduction.

Boiled gas generated in the ammonia storage tank 10 may constitute a free flow in the boil-off gas supply line (L30) by its own pressure, but is not limited thereto. The amount of boil-off gas may vary depending on the environment and operating conditions of the ship. When the amount of boil-off gas is small, the boil-off gas compressor 30 may be used to supply the boil-off gas to the SCR 23. For example, the boil-off gas supply line (L30) may be composed of a plurality of lines including a line having a boil-off gas compressor 30 and a line not provided, but is not limited thereto. The boil-off gas compressor 30 may pressurize and supply boil-off gas at a pressure required by the SCR 23 .

An boil-off gas supply line (L30) may be provided with a boil-off gas recovery line (L31) for supplying at least a portion of the boil-off gas to the boil-off gas treatment unit (31). The boil-off gas processing unit 31 may recover and process the boil-off gas when the SCR 23 does not need to operate because the amount of nitrogen oxides contained in the exhaust gas is less than a predetermined value. For example, the boil-off gas treatment unit 31 may be a re-liquefaction unit that re-liquefies the boil-off gas and return it to the ammonia storage tank 10, or a reformer that reforms the boil-off gas to produce hydrogen gas, but is not limited thereto. . The boil-off gas recovery line (L31) may branch from the boil-off gas supply line (L30) upstream of the boil-off gas compressor 30, and the supply to the boil-off gas treatment unit 31 may be controlled through the fifth valve (V5). there is.

A boil-off gas supply line (L30) may be provided with a boil-off gas branch line (L32) for supplying at least a portion of the boil-off gas to the catalyst unit 24. The boil-off gas branch line (L32) may process by supplying at least a portion of the boil-off gas to the catalyst part 24 according to the boil-off gas treatment conditions in the boil-off gas processing unit 31. The boil-off gas branch line (L32) may branch from the boil-off gas supply line (L30) upstream of the boil-off gas compressor 30, and the supply to the catalyst unit 24 may be controlled through the sixth valve (V6). .

Although not shown, the control unit adjusts the operation of the vessel configuration according to the present invention described above so that the amount of nitrogen oxides and ammonia included in the exhaust gas generated by the operation of the ammonia engine 20 is smaller than the respective emission standards. It can be treated and discharged. The control unit may receive information on the amount of nitrogen oxides and ammonia contained in the exhaust gas from the nitrogen oxide sensor 21 and the ammonia sensor 22 provided in the exhaust gas discharge line L20, and may be previously input or input. It is possible to compare the received information with the emission standard by each emission regulation.

For example, the control unit may operate the SCR 23 when the amount of nitrogen oxides contained in the exhaust gas is greater than a predetermined value. Operating the SCR (23) means supplying the exhaust gas to the SCR (23) and bringing it into contact with ammonia. In addition, the control unit may determine the flow rate of the boil-off gas supplied to the SCR 23 through the boil-off gas supply line L30 based on the amount of nitrogen oxides contained in the exhaust gas. In addition, the control unit may determine the flow rate of the boil-off gas supplied to the SCR 23 through the boil-off gas supply line L30 according to the amount of ammonia contained in the exhaust gas.

For example, the control unit may operate the catalyst unit 24 when the amount of ammonia contained in the exhaust gas is greater than a predetermined value. Operating the catalyst unit 24 means supplying exhaust gas to the catalyst unit 24 to contact the ammonia decomposition catalyst. In addition, the control unit may store information on ammonia slip that may occur during operation of the SCR 23 and determine whether the catalyst unit 24 is operated by considering the amount of ammonia included in the exhaust gas.

For example, when the amount of ammonia contained in the exhaust gas is greater than a predetermined value, the control unit controls the flow rate of the boil-off gas supplied from the boil-off gas supply line (L30) to the boil-off gas treatment unit (31) through the boil-off gas recovery line (L31). can increase If the amount of ammonia contained in the exhaust gas is large, the SCR 23 receives only a relatively small amount of boil-off gas and can treat nitrogen oxides in the exhaust gas. Boiled gas generated in the ammonia storage tank 10 is preferably recovered by the boil-off gas processing unit 31.

For example, the control unit increases the flow rate of ammonia supplied to the boil-off gas supply line (L30) through the return gas supply line (L42) when the flow rate of boil-off gas generated in the ammonia storage tank 10 is less than a predetermined value. can make it As the return gas is supplied and temporarily stored inside the collection tank 41, gaseous ammonia in the return gas is separated, and liquid ammonia naturally evaporates to generate boil-off gas. The gaseous ammonia collected in the collection tank 41 is supplied to the SCR 23 through the return gas supply line L42 and used, thereby facilitating the resupply of the return gas to the ammonia supply line L10, and the return gas The load applied to the cooler 40 can be reduced.

For example, the control unit may adjust the flow rate of ammonia supplied to the ammonia branch line L11 according to the flow rate of the return gas discharged from the ammonia engine 20 . Specifically, the flow rate of the return gas discharged from the ammonia engine 20 may vary according to the operating conditions of the ship, and when the flow rate of the return gas discharged from the ammonia engine 20 is small, the flow rate of the return gas discharged from the ammonia engine 20 is reduced through the collection tank 41. The flow rate of ammonia in the separable gas phase may also be reduced. The control unit may supply liquid ammonia to the vaporizer 14 through the ammonia branch line L11, forcibly vaporize it, and supply the liquid ammonia to the SCR 23.

As such, the control unit operates the SCR (23), the catalyst according to the amount of nitrogen oxides and ammonia included in the exhaust gas, the amount of return gas discharged from the ammonia engine 20, and the amount of boil-off gas generated from the ammonia storage tank 10. By implementing the control for adjusting the operation of the unit 24 and the vaporizer 14, it is possible to provide a ship that can satisfy exhaust gas emission standards while minimizing unnecessary waste of ammonia boil-off gas.

Figure 2 is a flow chart showing a control embodiment according to the operation of the ammonia engine in the ship according to the present invention.

The step of driving the ammonia engine and discharging the exhaust gas includes all of a series of operations in which the ammonia engine 20 receives ammonia through the ammonia supply line L10, burns it, and discharges the return gas and the exhaust gas, respectively. .

In the step of comparing NOx in the exhaust gas with the emission standard, the control unit measures the amount of nitrogen oxides contained in the exhaust gas through the nitrogen oxide sensor 21 provided on the exhaust gas discharge line L20 connected to the ammonia engine 20. This includes collecting information on the amount and comparing it to the emission standards set in the NOx emission regulation.

If the amount of NOx in the exhaust gas is greater than a predetermined value in the emission standards, the control unit may supply the exhaust gas to the SCR (23).

Thereafter, the control unit may further perform a step of comparing the amount of NH ₃ in the exhaust gas with the emission standard. The control unit may collect information on the amount of ammonia contained in the exhaust gas through the ammonia sensor 22 and compare it with emission standards determined in the ammonia emission regulation.

If the amount of NH ₃ in the exhaust gas is greater than a predetermined value in the emission standard, the control unit may further perform a step of comparing the amount of NH ₃ in the exhaust gas with the amount of NH ₃ required by the SCR 23 . If the amount of NH ₃ in the exhaust gas is greater than the amount of NH ₃ required by the SCR (23), nitrogen oxides can be reduced even if only the exhaust gas is supplied to the SCR (23) as it is, so the boil-off gas supply line (L30) Through this, the flow rate of boil-off gas supplied to the SCR (23) can be reduced or the supply can be stopped. In this case, the return gas discharged from the ammonia engine 20 is liquefied while passing through the return gas recovery line L40 and the ammonia supply line L10, and can be recycled to the ammonia engine 20.

If the amount of NH ₃ in the exhaust gas is less than the predetermined value in the emission standard, or if the amount of NH ₃ in the exhaust gas is greater than the predetermined value in the emission standard, but is less than the amount of NH ₃ required by the SCR (23), the control unit The catalyst inside the catalyst unit 24 may be protected by reducing the flow rate of the exhaust gas supplied to the catalyst unit 24 or by stopping the supply. The control unit supplies the boil-off gas to the SCR 23 through the boil-off gas supply line L30 to treat nitrogen oxides in the exhaust gas. At this time, the controller may further perform a step of comparing the amount of boil-off gas generated in the ammonia storage tank 10 and the supply amount of boil-off gas to be supplied to the SCR 23 . If the amount of boil-off gas is greater, the return gas discharged from the ammonia engine 20 may be liquefied while passing through the return gas recovery line L40 and the ammonia supply line L10 and recycled to the ammonia engine 20. there will be If the amount of boil-off gas is small, the return gas may be supplied to the SCR 23 through the boil-off gas supply line L30 through the return gas supply line L42. Additionally, the control unit may further perform a step of comparing the amount of return gas discharged from the ammonia engine 20, that is, the amount of return gas generated and the amount of return gas supplied to the SCR 23 through the return gas supply line L42. there is. If the amount of return gas is sufficient, the return gas is supplied to the SCR (23), and if the amount of return gas is insufficient, the ammonia in the ammonia storage tank (10) is supplied to the ammonia branch line (L11) for forced vaporization in the vaporizer (14). After doing this, it can be supplied to the SCR (23) via the boil-off gas supply line (L30).

When the amount of NOx in the exhaust gas is less than a predetermined value in the emission standard, the control unit may stop supplying the exhaust gas to the SCR (23).

Thereafter, the control unit may further perform a step of comparing the amount of NH ₃ in the exhaust gas with the emission standard. When the amount of NH ₃ in the exhaust gas is greater than a predetermined value in the emission standard, the control unit may supply the exhaust gas to the catalyst unit 24 to decompose ammonia in the exhaust gas. When the amount of NH ₃ in the exhaust gas is less than a predetermined value in the emission standard, the control unit may reduce the amount of exhaust gas supplied to the catalyst unit 24 or stop supplying the exhaust gas. In either case, since the SCR (23) is not operated, the boil-off gas generated in the ammonia storage tank 10 is supplied to the SCR (23) through the boil-off gas supply line (L30), instead of the boil-off gas recovery line (L31). It can be supplied to the boil-off gas processing unit 31 through. In addition, the return gas discharged from the ammonia engine 20 is not supplied to the return gas supply line L42, but is liquefied while passing through the return gas recovery line L40 and the ammonia supply line L10 and recirculated to the ammonia engine 20. You can go through the process of becoming.

Although the exhaust gas treatment process according to the condition of the ship according to the present invention has been described through the flowchart as described above, it will be understood that the processing step of the control unit is not limited to the above-described embodiment.

Of course, the present invention is not limited to the above-described embodiment, and may include a combination of the above embodiments or a combination of at least one of the above embodiments and known technology as another embodiment.

In the above, the present invention has been described centering on the embodiments of the present invention, but these are only examples and do not limit the present invention, and those skilled in the art to which the present invention belongs do not deviate from the essential technical content of the present embodiment. It will be appreciated that various combinations or modifications and applications not exemplified in the embodiments are possible within the range. Therefore, technical contents related to modifications and applications that can be easily derived from the embodiments of the present invention should be construed as being included in the present invention.

10: ammonia storage tank 11: pump
12: heat exchanger 13: high pressure pump
14: carburetor 20: ammonia engine
21: nitrogen oxide sensor 22: ammonia sensor
23: SCR 24: catalyst part
25: exhaust gas discharge unit 30: boil-off gas compressor
31: boil-off gas processing unit 40: return gas cooler
41: collection tank
L10: ammonia supply line L11: ammonia branch line
L20: exhaust gas discharge line L30: boil-off gas supply line
L31: boil-off gas recovery line L32: boil-off gas branch line
L40: return gas recovery line L41: return gas branch line
L42: Return gas supply line V1 to V8: 1st to 8th valves

Claims (8)

As a ship propelled by using ammonia as fuel,
An ammonia supply line for supplying ammonia stored in the ammonia storage tank to an ammonia engine;
a return gas recovery line for transferring return gas discharged from the ammonia engine and mixed with oil to the ammonia supply line;
a collection tank separating the oil mixed with the return gas flowing through the return gas recovery line;
an exhaust gas discharge line having an SCR reducing nitrogen oxides in exhaust gas discharged from the ammonia engine; and
A boil-off gas supply line for supplying boil-off gas generated in the ammonia storage tank to the SCR,
The SCR is
A ship receiving the boil-off gas from the boil-off gas supply line and injecting the boil-off gas into the exhaust gas discharged from the ammonia engine so that it is mixed with the exhaust gas. According to claim 1,
The ammonia supply line,
Including a heat exchanger and a high-pressure pump that heats ammonia as a heat medium,
The return gas recovery line,
A vessel comprising a return gas cooler provided downstream of the collection tank and connected to the ammonia supply line upstream of the high-pressure pump. According to claim 1,
Ships further comprising a control unit for operating the SCR when the amount of nitrogen oxides contained in the exhaust gas is greater than a predetermined value. According to claim 1,
The exhaust gas discharge line,
It is provided downstream of the SCR and further includes a catalyst for decomposing ammonia in exhaust gas,
A ship further comprising a control unit for operating the catalyst unit when the amount of ammonia contained in the exhaust gas is greater than a predetermined value. According to claim 1,
Ship further comprising a control unit for adjusting the flow rate of the boil-off gas supplied to the SCR through the boil-off gas supply line according to the amount of ammonia contained in the exhaust gas. According to claim 5,
Further comprising a boil-off gas treatment unit for recovering boil-off gas generated in the ammonia storage tank,
The control unit,
If the amount of ammonia contained in the exhaust gas is greater than a predetermined value, the flow rate of the boil-off gas supplied to the boil-off gas treatment unit is increased. According to claim 1,
a return gas supply line for transferring gaseous ammonia separated from the collection tank to the boil-off gas supply line; and
A ship further comprising a control unit for increasing the flow rate of ammonia supplied through the return gas supply line when the flow rate of boil-off gas generated in the ammonia storage tank is less than a predetermined value. According to claim 1,
an ammonia branch line branching from the ammonia supply line and vaporizing ammonia and passing it to the boil-off gas supply line; and
A ship further comprising a control unit for adjusting the flow rate of ammonia supplied to the ammonia branch line according to the flow rate of the return gas discharged from the ammonia engine.

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